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Markov model

P D S N Somarathna, Budiman Minasny, Brendan P Malone, Uta Stockmann, Alex B McBratney
Spatial modelling of environmental data commonly only considers spatial variability as the single source of uncertainty. In reality however, the measurement errors should also be accounted for. In recent years, infrared spectroscopy has been shown to offer low cost, yet invaluable information needed for digital soil mapping at meaningful spatial scales for land management. However, spectrally inferred soil carbon data are known to be less accurate compared to laboratory analysed measurements. This study establishes a methodology to filter out the measurement error variability by incorporating the measurement error variance in the spatial covariance structure of the model...
March 8, 2018: Science of the Total Environment
Xiaolei Xie, Tianhua He, Jian Kang, David S Siscovick, Yan Li, José A Pagán
China has the largest population of adults with hypertension in the world. Recent clinical trials have shown that intensive hypertension control can help patients achieve lower blood pressure and reduce the incidence of major cardiovascular disease (CVD) events, but this level of hypertension control also incurs additional costs to patients and society and may result in a substantial increase in adverse events. The objective of this study is to assess the cost-effectiveness of intensive hypertension control to inform health policymakers and health care delivery systems in China in their decision-making regarding hypertension treatment strategies...
March 8, 2018: Preventive Medicine
Christine M Custer, Thomas W Custer, Matthew A Etterson, Paul M Dummer, Diana Goldberg, J Christian Franson
During 2010-2014, tree swallow (Tachycineta bicolor) reproductive success was monitored at 68 sites across all 5 Great Lakes, including 58 sites located within Great Lakes Areas of Concern (AOCs) and 10 non-AOCs. Sample eggs were collected from tree swallow clutches and analyzed for contaminants including polychlorinated biphenyls (PCBs), dioxins and furans, polybrominated diphenyl ethers, and 34 other organic compounds. Contaminant data were available for 360 of the clutches monitored. Markov chain multistate modeling was used to assess the importance of 5 ecological variables and 11 of the dominant contaminants in explaining the pattern of egg and nestling failure rates...
March 9, 2018: Ecotoxicology
Yang Meng, Nadine Hertel, John Ellis, Edith Morais, Helen Johnson, Zoe Philips, Neil Roskell, Andrew Walker, Dawn Lee
BACKGROUND: Nivolumab was the first programmed death receptor 1 (PD-1) immune checkpoint inhibitor to demonstrate long-term survival benefit in a clinical trial setting for advanced melanoma patients. OBJECTIVE: To evaluate the cost effectiveness of nivolumab monotherapy for the treatment of advanced melanoma patients in England. METHODS: A Markov state-transition model was developed to estimate the lifetime costs and benefits of nivolumab versus ipilimumab and dacarbazine for BRAF mutation-negative patients and versus ipilimumab, dabrafenib, and vemurafenib for BRAF mutation-positive patients...
March 9, 2018: European Journal of Health Economics: HEPAC: Health Economics in Prevention and Care
Bob Rehder
Although many theories of causal cognition are based on causal graphical models, a key property of such models-the independence relations stipulated by the Markov condition-is routinely violated by human reasoners. This article presents three new accounts of those independence violations, accounts that share the assumption that people's understanding of the correlational structure of data generated from a causal graph differs from that stipulated by causal graphical model framework. To distinguish these models, experiments assessed how people reason with causal graphs that are larger than those tested in previous studies...
March 6, 2018: Cognitive Psychology
Fabian Paul, Frank Noé, Thomas R Weikl
Unstructured protein and peptides typically fold during binding to ligand proteins. A challenging problem is to identify the mechanism and kinetics of these binding-induced folding processes in experiments and atomistic simulations. In this article, we present a detailed picture for the folding of the inhibitor peptide PMI into a helix during binding to the oncoprotein fragment25-109 Mdm2 obtained from atomistic, explicit-water simulations and Markov state modeling. We find that binding-induced folding of PMI is highly parallel and can occur along a multitude of pathways...
March 9, 2018: Journal of Physical Chemistry. B
Neethu Mariam Joy, S Umesh
Assistive speech-based technologies can improve the quality of life for people affected with dysarthria, a motor speech disorder. In this paper, we explore multiple ways to improve Gaussian mixture model and deep neural network (DNN) based hidden Markov model (HMM) automatic speech recognition systems for TORGO dysarthric speech database. This work shows significant improvements over the previous attempts in building such systems in TORGO. We trained speaker-specific acoustic models by tuning various acoustic model parameters, using speaker normalized cepstral features and building complex DNN-HMM models with dropout and sequence-discrimination strategies...
March 2018: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Michele Molinari, Chethan Puttarajappa, Martin Wijkstrom, Armando Ganoza, Roberto Lopez, Amit Tevar
BACKGROUND: Recent studies have reported a significant decrease in wound problems and hospital stay in obese patients undergoing renal transplantation by robotic-assisted minimally invasive techniques with no difference in graft function. OBJECTIVE: Due to the lack of cost-benefit studies on the use of robotic-assisted renal transplantation versus open surgical procedure, the primary aim of our study is to develop a Markov model to analyze the cost-benefit of robotic surgery versus open traditional surgery in obese patients in need of a renal transplant...
March 8, 2018: JMIR Research Protocols
Marc A Dämgen, Philip C Biggin
Many proteins that are central to key aspects of neurobiology undergo conformational changes as part of their function, usually in response to a stimulus. Often, these proteins are embedded within a membrane, which creates particular experimental challenges to surmount. This has resulted in computational methods providing a valuable complementary tool for some time now, especially in the development of working models at atomic resolution. Indeed, molecular dynamics MD) simulations are now routinely applied to new structures, either as part of the initial analysis or as part of an automated pipeline...
March 5, 2018: Neuroscience Letters
Scott C Faucett, Benjamin Peter Geisler, Jorge Chahla, Aaron J Krych, Peter R Kurzweil, Abigail M Garner, Shan Liu, Robert F LaPrade, Jan B Pietzsch
BACKGROUND: Medial meniscus root tears are a common knee injury and can lead to accelerated osteoarthritis, which might ultimately result in a total knee replacement. PURPOSE: To compare meniscus repair, meniscectomy, and nonoperative treatment approaches among middle-aged patients in terms of osteoarthritis development, total knee replacement rates (clinical effectiveness), and cost-effectiveness. STUDY DESIGN: Meta-analysis and cost-effectiveness analysis...
March 1, 2018: American Journal of Sports Medicine
Meysam Hashemi, Axel Hutt, Laure Buhry, Jamie Sleigh
Mathematical modeling is a powerful tool that enables researchers to describe the experimentally observed dynamics of complex systems. Starting with a robust model including model parameters, it is necessary to choose an appropriate set of model parameters to reproduce experimental data. However, estimating an optimal solution of the inverse problem, i.e., finding a set of model parameters that yields the best possible fit to the experimental data, is a very challenging problem. In the present work, we use different optimization algorithms based on a frequentist approach, as well as Monte Carlo Markov Chain methods based on Bayesian inference techniques to solve the considered inverse problems...
March 7, 2018: Neuroinformatics
Lan Yang, Jing Wang, Juan Cheng, Yuan Wang, Wenli Lu
BACKGROUND: We aimed to clarify the feasibility of a community-based screening strategy for breast cancer in Tianjin, China; to identify the factors that most significantly influenced its feasibility; and to identify the reference range for quality control. METHODS: A state-transition Markov model simulated a hypothetical cohort of 100,000 healthy women, the start aged was set at 35 years and the time horizon was set to 50 years. The primary outcome for the model was the incremental cost-utility ratio (ICUR), defined as the program's cost per quality-adjusted life year (QALY) gained...
March 7, 2018: BMC Cancer
Petra Baji, László Gulácsi, Valentin Brodszky, Zsuzsanna Végh, Silvio Danese, Peter M Irving, Laurent Peyrin-Biroulet, Stefan Schreiber, Fanni Rencz, Péter L Lakatos, Márta Péntek
Background: In clinical practice, treatment sequences of biologicals are applied for active fistulising Crohn's disease, however underlying health economic analyses are lacking. Objective: The purpose of this study was to analyse the cost-effectiveness of different biological sequences including infliximab, biosimilar-infliximab, adalimumab and vedolizumab in nine European countries. Methods: A Markov model was developed to compare treatment sequences of one, two and three biologicals from the payer's perspective on a five-year time horizon...
March 2018: United European Gastroenterology Journal
Miguel Areia, Manon Cw Spaander, Ernst J Kuipers, Mário Dinis-Ribeiro
Background: Endoscopic screening for gastric cancer is debatable in countries with an intermediate risk. Objective: The objective of this article is to determine the cost-utility of screening strategies for gastric cancer in a European country. Methods: We conducted a cost-utility analysis using a Markov model comparing three screening strategies versus no screening: stand-alone upper endoscopy, endoscopy combined with a colorectal cancer screening colonoscopy after a positive faecal occult blood test or pepsinogens serologic screening...
March 2018: United European Gastroenterology Journal
Stefan Walzer, Daniel Dröschel, Lutz Vollmer, Leanne Atkin, Karen Ousey
OBJECTIVE: Venous leg ulcers (VLUs) cause significant pain and suffering for patients. Additionally, they place considerable financial and service burden on the National Health Service (NHS). A large proportion of VLUs do not heal within the standard time frame of 16-24 weeks, resulting in static wounds which commonly have issues with increasing exudate production. As the NHS continues to face times of austerity, services need to find solutions to be able to reduce costs and release nursing time while maintaining standards of care...
March 2, 2018: Journal of Wound Care
Xulong Wang, Vivek M Philip, Guruprasad Ananda, Charles C White, Ankit Malhotra, Paul J Michalski, Krishna R Murthy Karuturi, Sumana R Chintalapudi, Casey Acklin, Michael Sasner, David A Bennett, Philip L De Jager, Gareth R Howell, Gregory W Carter
Recent technical and methodological advances have greatly enhanced genome-wide association studies (GWAS). The advent of low-cost whole-genome sequencing facilitates high-resolution variant identification, and the development of linear mixed models (LMM) allows improved identification of putatively causal variants. While essential for correcting false positive associations due to sample relatedness and population stratification, LMMs have commonly been restricted to quantitative variables. However, phenotypic traits in association studies are often categorical, coded as binary case-control or ordered variables describing disease stages...
March 5, 2018: Genetics
Giovanni B Brandani, Toru Niina, Cheng Tan, Shoji Takada
While nucleosomes are highly stable structures as fundamental units of chromatin, they also slide along the DNA, either spontaneously or by active remodelers. Here, we investigate the microscopic mechanisms of nucleosome sliding by multiscale molecular simulations, characterizing how the screw-like motion of DNA proceeds via the formation and propagation of twist defects. Firstly, coarse-grained molecular simulations reveal that the sliding dynamics is highly dependent on DNA sequence. Depending on the sequence and the nucleosome super-helical location, we find two distinct types of twist defects: a locally under-twisted DNA region, previously observed in crystal structures, and a locally over-twisted DNA, an unprecedented feature...
February 28, 2018: Nucleic Acids Research
Kathryn E Hendee, Elena A Sorokina, Sanaa S Muheisen, Linda M Reis, Rebecca C Tyler, Vujica Markovic, Goran Cuturilo, Brian A Link, Elena V Semina
The PITX2 (paired-like homeodomain 2) gene encodes a bicoid-like homeodomain transcription factor linked with several human disorders. The main associated congenital phenotype is Axenfeld-Rieger syndrome, type 1 (ARS), an autosomal dominant condition characterized by variable defects in the anterior segment of the eye, an increased risk of glaucoma, craniofacial dysmorphism and dental and umbilical anomalies; in addition to this, one report implicated PITX2 in ring dermoid of the cornea and a few others described cardiac phenotypes...
March 1, 2018: Human Molecular Genetics
Faustin Habyarimana, Temesgen Zewotir, Shaun Ramroop
The main objective of this study was to assess the risk factors and spatial correlates of domestic violence against women of reproductive age in Rwanda. A structured spatial approach was used to account for the nonlinear nature of some covariates and the spatial variability on domestic violence. The nonlinear effect was modeled through second-order random walk, and the structured spatial effect was modeled through Gaussian Markov Random Fields specified as an intrinsic conditional autoregressive model. The data from the Rwanda Demographic and Health Survey 2014/2015 were used as an application...
March 1, 2018: Journal of Interpersonal Violence
Katherine M Thieltges, Dragana Avramovic, Chayne L Piscitelli, Sandra Markovic-Mueller, Hans Kaspar Binz, Kurt Ballmer-Hofer
Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel development upon activation of three receptor tyrosine kinases (VEGFRs). The extracellular domain of VEGFRs consists of seven Ig-homology domains, of which D2-3 form the ligand-binding site, while the membrane proximal domains D4-7 are involved in homotypic interactions in ligand-bound receptor dimers. Based on low-resolution structures, we identified allosteric sites in D4-5 and D7 of vascular endothelial growth factor receptor 2 (VEGFR-2) accomplishing regulatory functions...
March 3, 2018: Angiogenesis
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